Oral rehydration solution (ORS) is recommended for treatment and prevention of dehydration due to acute gastroenteritis in infants and children. Acute diarrhoea leads to zinc depletion in infants, and zinc is recommended by the World Health Organization in the treatment of acute gastroenteritis in infants and children. However, the efficacy of zinc supplementation to children with acute gastroenteritis in more affluent settings is unclear. Selected strains of probiotics, including L. reuteri ATCC 55730, have been shown in several studies to shorten the duration of diarrhoea by about 24 hours, and also to attenuate symptom severity. If probiotics are given within 60 hours from onset of symptoms the duration can be reduced even more. Lactobacillus reuteri (L. reuteri) has been shown to reduce the duration and severity of acute gastroenteritis in children aged 6-36 months. In these studies L. reuteri was proven to have clinical effect on diarrhoea of both bacterial and viral (rotavirus) origin. In humans, L. reuteri strain DSM 17938 has recently been shown to reduce the duration of watery diarrhoea by 1.2 days among 6-36 mo old Italian children with acute gastroenteritis treated in hospital.